PT-2026-79778

justhtml through 1.9.1 fixed in 1.10.0 is vulnerable to uncontrolled recursion leading to denial of service. During JustHTML construction, TreeBuilder.finish unconditionally calls populate selectedcontent, which recursively traverses the DOM tree via find elements/ find element without a depth...

PT-2026-79777

Name of the Vulnerable Software and Affected Versions justhtml versions prior to 1.12.0 Description A mutation cross-site scripting mXSS issue exists during the serialization of raw-text elements, such as and . When the sanitize dom function processes a DOM tree using a custom policy that retains...

PT-2026-79775

Name of the Vulnerable Software and Affected Versions justhtml versions prior to 1.16.0 Description Multiple HTML sanitization bypass issues allow active or dangerous content, such as script or style tags, to survive the sanitization process, potentially leading to cross-site scripting. These...

PT-2026-79768

justhtml before 1.18.0 contains multiple low-severity denial-of-service issues in CSS selector handling and linkification. Applications that evaluate attacker-controlled selector strings via query, matches, or selector-based transforms, run selector matching over very large untrusted documents,...

GHSA-JF6W-2MVX-633J justhtml: to_markdown() code-span blank-line breakout enables XSS

justhtml: tomarkdown code-span blank-line breakout enables XSS Summary In justhtml 0.9.0 through 1.21.0, tomarkdown renders text and text inside a link as an inline Markdown code span whose only protection is backtick-fence length. A blank line \n\n in that text terminates the inline span in any...

Infinite loop

Overview justhtml is an A pure Python HTML5 parser that just works. Affected versions of this package are vulnerable to Infinite loop in the handling of CSS selectors and linkification processes. An attacker can cause excessive CPU or memory consumption by supplying specially crafted selector...

justhtml introduces denial-of-service hardening

Summary justhtml 1.18.0 fixes multiple low-severity denial-of-service hardening issues in CSS selector handling and linkification. These issues are availability concerns. They do not allow script execution, data disclosure, or sanitizer bypass by themselves. Affected versions - justhtml 1.18.0...

GHSA-R8CJ-3554-33MR justhtml introduces denial-of-service hardening

Summary justhtml 1.18.0 fixes multiple low-severity denial-of-service hardening issues in CSS selector handling and linkification. These issues are availability concerns. They do not allow script execution, data disclosure, or sanitizer bypass by themselves. Affected versions - justhtml 1.18.0...

Modification of Assumed-Immutable Data (MAID)

Overview justhtml is an A pure Python HTML5 parser that just works. Affected versions of this package are vulnerable to Modification of Assumed-Immutable Data MAID through the sanitize, sanitizedom, and JustHTML..., sanitize=True paths in src/justhtml/sanitize.py. An attacker can bypass intended...

GHSA-4P64-V8F5-R2GX Multiple security fixes in justhtml

Summary justhtml 1.16.0 fixes multiple security issues in sanitization, serialization, and programmatic DOM handling. Most of these issues affected one of these advanced paths rather than ordinary parsed HTML with the default safe settings: - programmatic DOM input to sanitize or sanitizedom -...

Cross-site Scripting (XSS)

Overview justhtml is an A pure Python HTML5 parser that just works. Affected versions of this package are vulnerable to Cross-site Scripting XSS in the handling of URL sanitization helpers, HTML serialization, Markdown passthrough, and custom sanitization-policy edge cases. An attacker can execut...

GHSA-R758-8HXW-4845 justhtml: Mutation XSS with custom foreign-namespace sanitization policies

Summary A parser-differential / mutation XSS issue was found in justhtml when using a custom sanitization policy that preserves foreign namespaces such as SVG or MathML. Under these custom settings, specially crafted input could sanitize into HTML that looked safe at first, but became unsafe when...

Cross-site Scripting (XSS)

Overview justhtml is an A pure Python HTML5 parser that just works. Affected versions of this package are vulnerable to Cross-site Scripting XSS via the custom SanitizationPolicy if configured with dropforeignnamespaces=False or allowlisted foreign elements such as MathML or SVG or raw-text...

justhtml: Mutation XSS with custom foreign-namespace sanitization policies

Summary A parser-differential / mutation XSS issue was found in justhtml when using a custom sanitization policy that preserves foreign namespaces such as SVG or MathML. Under these custom settings, specially crafted input could sanitize into HTML that looked safe at first, but became unsafe when...

GHSA-5VP3-3CG6-2RQ3 JustHTML is vulnerable to XSS via code fence breakout in <pre> content

Summary tomarkdown is vulnerable when serializing attacker-controlled content. The handler emits a fixed three-backtick fenced code block, but writes decoded text content into that fence without choosing a delimiter longer than any backtick run inside the content. An attacker can place backticks...

JustHTML is vulnerable to XSS via code fence breakout in <pre> content

Summary tomarkdown is vulnerable when serializing attacker-controlled content. The handler emits a fixed three-backtick fenced code block, but writes decoded text content into that fence without choosing a delimiter longer than any backtick run inside the content. An attacker can place backticks...

JustHTML has a Sanitizer Bypass (in Markdown)

Summary tomarkdown does not sufficiently escape text content that looks like HTML. As a result, untrusted input that is safe in tohtml can become raw HTML in Markdown output. This is not specific to tokenizer raw-text states like , , or , although those states can trigger the behavior. The root...

Cross-site Scripting (XSS)

Overview justhtml is an A pure Python HTML5 parser that just works. Affected versions of this package are vulnerable to Cross-site Scripting XSS in the tomarkdown function. An attacker can inject arbitrary HTML content by supplying specially crafted input that includes HTML-significant characters...

GHSA-3RCM-VJRC-P45J JustHTML has a Sanitizer Bypass (in Markdown)

Summary tomarkdown does not sufficiently escape text content that looks like HTML. As a result, untrusted input that is safe in tohtml can become raw HTML in Markdown output. This is not specific to tokenizer raw-text states like , , or , although those states can trigger the behavior. The root...

GHSA-V7CF-C9RM-WM3J Uncontrolled recursion DoS in JustHTML() via deeply nested HTML

Summary justhtml through 1.9.1 allows denial of service via deeply nested HTML. During parsing, JustHTML.init always reaches TreeBuilder.finish, which unconditionally calls populateselectedcontent. That function recursively traverses the DOM via findelements / findelement without a depth bound,...